Air filtration masks (referred to herein as “filter masks”) are widely used to protect people from air borne contaminants and gasses. For example, air borne dust particles are a known hazard commonly on work sites. Consequently, such workers normally wear filter masks to avoid inhaling the dust particles. To that end, filter masks used in this application are manufactured with a filter material specified to prevent, among other things, a substantial majority of dust particles from being inhaled by the worker.
In addition to primarily protecting inhaled air, some filter masks are specifically manufactured to filter both inhaled and exhaled air. For example, hospital staff often wear filter masks to prevent both their germs from infecting patients, and patients' germs from infecting them.
There is a need in the art to improve the filtration efficiency of filter masks. Accordingly, filter masks with multiple filter layers have been developed for that purpose. Multiple filter layer filter masks typically filter particles and gasses more efficiently than many types of single filter layer filter masks. Use of multiple filter layers, however, undesirably increases the air resistance through the filter mask. Consequently, a person wearing the filter mask-may have a more difficult time breathing. In fact, due to reduced amount of breathable air, some people can become dizzy when wearing multiple layer filter masks.
To overcome this problem while still providing improved filtration efficiency, filter masks have been developed to increase filter area, thus improving performance. Manufacture of such filter masks, however, can be more complex than filter masks with multiple filter layers. Sometimes, increasing the area can cause portions of the single layer filter layer to overlap. Overlap effectively increases the thickness of the filter layer, thus causing the same air resistance problem as discussed above.